Holidaymakers who have taken out travel insurance to cover cancellation in the event of swine flu could find themselves out of pocket if the small print has an exclusion for pandemics.

Insurers will not pay out on those policies that contain this clause should you have to cancel a trip due to swine flu. Holidaymakers are being urged to check their policy and contact their insurer if in doubt.

The Association of British Insurers (ABI) says it knows two of its members have a pandemic exclusion. However, those firms have agreed to provide cover for swine flu cases, and others will be under pressure to do the same.

Worries as to whether policies would cover swine flu cancellations reached a peak last week as it became clear increasing numbers of holidaymakers will have to cancel their trips if they are diagnosed with, or even suspected of suffering from, the virus.

Some airlines are now turning away passengers if they believe them to be infected.

A good policy should cover the cost of a holiday if it is cancelled because someone is too ill to travel, as well as the cost of medical treatment abroad and any associated delays caused by getting an illness on holiday.

Those who suspect they are suffering from the illness should contact their doctor or the National Pandemic Flu Service (0800 1513513), which went live on Thursday. If your doctor believes you have swine flu, that information should be enough for an insurer to start the claim process, and completed once the doctor sends written confirmation.

If you are diagnosed via the National Pandemic Flu Service, you will not need a note from your doctor.

"We understand the service will only authorise an anti-flu prescription to people who are genuinely displaying symptoms of swine flu," said Nick Starling, the ABI's director of general insurance and health.

"On that basis, travel insurers will accept an individual's unique ID number generated by the National Flu Service, together with the label on their anti-flu drugs which states their name and date of issue, as proof of diagnosis to validate a claim for cancellation."

If travelling with your spouse, children or other close relatives on one policy, the payout covers all of you.

However travel insurers will not pay if you have a "general disinclination" to make a journey because of the virus.